This invention relates generally to cardiac pacing and mapping systems used in diagnosing and treating cardiac conditions. The invention also relates to electronic switching systems for programmably intercoupling multiple inputs with multiple outputs in pre-selected configurations. More particularly, the invention relates to an application specific integrated circuit (ASIC) operable to configure multiple input electrodes for cardiac signal recording and analysis or stimulation based on the immediate necessities of a particular electrophysiological procedure.
Advances in the cardiac mapping and pacing art have made it possible to acquire cardiac data through multiple channels. Known cardiac mapping and pacing catheters contain as many as sixty-four individual electrodes, each of which can be used for both mapping and pacing. Along with the flexibility, resolution and utility provided by such catheters comes the need to process the resulting data in an efficient, organized manner.
Various data acquisition systems have been developed for processing data acquired during cardiac mapping and pacing procedures. Typically, such systems record data through multiple recording inputs and process the data to assist the physician in making a diagnosis and rendering treatment. Some systems also include circuitry for generating pacing pulses that can be applied to the heart. Although effective in their intended application, known data acquisition systems become limited in their capabilities as advances in cardiac catheters provide ever increasing amounts of data. Many known data acquisition systems only support input from up to twenty-four electrodes and are not directly useful with catheters containing more than twenty-four electrodes. Because data acquisition systems are larger, more complicated and more expensive than the cardiac catheters used in mapping and pacing, it is impractical to redesign a data acquisition system each time an advance in the catheter art enables the acquisition of still more data. Nor is it economically sound for health care providers to retire still serviceable existing systems in favor of the latest model each time a new catheter is introduced. As advances are made in the catheter art, a need develops for adapting the new catheter to use with existing data acquisition systems.
The advances that can increase the demands on a data acquisition system are many and varied. For example, "impedance mapping" techniques have been developed wherein the resistivity of cardiac tissue is measured using an injected current. Infarcted cardiac tissue is detected by virtue of the lower electrical resistivity such tissue displays relative to healthy or normal tissue. Known data acquisition systems do not provide for the flexible electrode configuring and sequencing required or desirable in impedance mapping procedures. Similarly, existing data acquisition systems do not provide for automated sequencing and configuration of pacing electrodes. Nor do such systems provide for automatic detection of open or shorted electrodes. As the number of electrodes used in a procedure increases, so does the possibility of such malfunctions. Existing systems do not automatically and continuously monitor the electrodes to warn the physician in the event some of the electrodes are open or shorted. Absent an appropriate warning that some electrodes are no longer suitable for therapy or diagnosis, the delivery of effective therapy can be unknowingly prevented.
Known data acquisition systems for recording electrophysiological (EP) information have previously achieved switching capability through use of analog switch chips or mechanical switches in the system's signal conditioning circuitry. The ability to increase the number of potential electrode inputs was dependent on the particular system. Prior data acquisition systems were not designed for use with catheters containing large numbers of electrodes and did not provide the flexibility for configuring electrode subsets. Such prior systems also lacked open/short detection and automated pacing/switching capabilities.